Duplex wireless system.



J. R. CARSON.

DUPLEX WIRELESS SYSTEM.

APPLICATION I fILEn sEPT.21.I9I5.

l.,88,531. PatentedJune27,1916. v

arney.

'I'OHN' R. CARSON, 0F NEW YORK, N. Y., .ASSIGNR TO AMERICAN TELEPHONE AND TELEG-BAPH COMPANY, A CRPORATON 0F NEW YORK.k

DUPLEX WIRELESS SYSTEM.

Specification of Letters Patent.

Patented June a7, 191e.

Application filed September 2'?, 1915. Serial No. 52,860.

To all whom t may concern.'

system for the simultaneous transmission and reception of signals in which dilferent wave lengths are employed for the transmitted and received signals.

Heretofore, in actual practice, it has been p customary to alternatively put the transmitting and the receiving circuit 'proper into operative connection with the antenna by means of `a switching arrangement.

It is the object of this invention to provide a means whereby two-way or duplex communication between two wireless stations may be carried on automatically in a manner analogous to that at present obtaining in connner'cial telephone and duplex telegraph systems. l It is well known that, in wireless telegraphy and telephony, the magnitude of the transmitted current is enormously greater than the received current, their ratio being of the order of one millionv to one. This enormous ratio renders inapplicable to wireless systems, methods which are employed successfully in wire telegraph and telephone systems. The wireless system, is, however, differentiated in the following two important respects from the ordinary wire telegraph and telephone systems; first, energy is transmittedl and received at definite constant frequencies or wave' lengths; and, secondly, resonant tuned circuits are employed. The present invention is based on these two facts.

The requirements of a successful wireless duplex system are: rst, that the system have two resonant frequencies or wave.

lengths, to one of which'the transmitting system proper is tuned, and to the. other of which the receiving system proper is tuned; and secondly, that the receiving system proper be very etliciently screened or protected from electromagnetic induction from the transmitting system. The manner in 'which this invention satisfies these requirements and the invention itself may best` panying drawing lwhich is a diagram of a system embodyingthis invention.

Referring to lsaid drawing, 1 is the antenna circuit, and 2 is an auxiliary branch circuit containing a resistance 3, inductance 4, and capacity 5, by means of which the antenna branch 1, and branch 2 may be ad- ]usted to have the same impedance at the transmission wave length., A branch 6 connects the system to ground, and contains the primary of an oscillation transformer 7 which. couples the transmitting circuit 18 to the antenna system. The transmitting circuit is shown, for convenience, as energized by a high frequency generator 17.

A'receiving oscillation circuit 8 contains an adjustable condenser 9 and the anti-resonant set 10. Said receiving circuit is in-v ductively connected to the antenna by means i of inductance coils 11 and 13 and to the branch 2 by means of the inductance coils 12 i and 14, said coils being similar and equal.

Across condenser 9 is connected the input side o-f a detector 15 preferably of the vacuum tube type, whose output side is operatively-connected to a telephone receiver 16. It will be understood, of course, that the application of the present system is not limited toany particular type of receiving apparatus.

It is evident that the addition of the auxiliary branch circuit 2 gives the system two degrees of freedom and therefore two resonant wave lengths. One of these resonant wave lengths is employed for transmission and the other for reception of signals.

The operation ofthe organization shown, with regard to transmission of signals, is as follows :-T he system is excited or energized by a sourcebf high frequency energy, conventionally represented by thehigh frequency generator 17, through the oscillation transformer 7. Since the two branches 1 and 2 have the same impedance, the current l divides equally between said two branches. The transmission current, therefore, induces equal and opposing voltage in the coils 11 and 12 which are coupled to coils 13 and 14 respectively; and, hence, if the two branches are balanced, the resultant voltage and current in the coupled receiving circuit 8 is zero. An exact balance of the. two branches is diiiicult and indeed impracticable to obtain and maintain, and hence a slight degree of unbalance must be expected and.

.,...e .se a 12a sta-.ss

f guarde against. The efect of anv unbalance is minimized by tuning the receivlng circuitS to the wave length of reception; wherefore, the receiving circuit o l'ers a hlgh impedance to currents of the transmitted Wave lengths. This impedance at the transmission wave length may be made very large by including in the receiving'circuit the set 10, which is adjusted to anti-resonance to the transmission wave length. rlhe receiving circuit as 'a whole is tuned to the reception wave length. l

It will be evident from the fqregoing description that when impulses originate in branch 6, branches 1 and 2 are symmetrically related to said impulses and, since the impedances of said branches 1 `and 2are equal, equal currents flow in said branches with the result that no current flows in the receiving circuit 8. During reception of signals, the energy from the incident waves is absorbed by the antenna. rlhe received impulses therefore originate in branch 1, A and branches l and 2 are not symmetrical with respect'to said received impulses. rlhe currents, therefore, in branches land 2, corresponding to the received signals, are not equal, and the receiving circuit 8 is not balanced with respect to said signals. Since said receiving circuit 8 is tuned to the wave length of said received signals it is ,strongly responsive vthereto and the receiver 16 1s therefore energized, independently of the fact that the system may be -simultaneously radiating energy at a different wave length.

l claim: l. A duplex wireless signaling system employing dierent wavelengths for the transmission and reception of signals comprising I an antenna circuit, an auxiliary branch circuit having substantially the same impedance as said antenna circuit and in parallel therewith with respect to the transmission current; an oscillation circuit di'erentially connected to both of said circuit, said oscillation circuit having a high impedance for currents of the transmission frequency and low impedance for currents of the reception frequency, and a receiving device operatively connected to said oscillation circuit.

2. A duplex wireless `telegraph 0r tele-` phone system employingl) diierent wave lengths 'for the transmission and reception of signals comprising a branch circuit in- :creator cluding vthe coupling inductance coil, a second branch circuit,-including the rimary ofa transmitting oscillation trans ormer, connecting said antenna branch to ground, and an auxiliary branch circuit connected to ground and to the common point of said two branch circuits, said auxiliary branch circuit including the primary of a couplingy inductance coil and also including resistance, inductance and capacity elements so adjusted that 'the said auxiliary branch circuit has the sanfe impedance as the antenna branch circuit, and a Yreceiving circuit coupled by means of said ranch antenna andthe primary of a Kcluding the antenna and the primary of a 'coupling inductance coil, a second circuit including the primary of a transmitting oscillation transformer, and connecting said antenna branch to ground, and an auxiliary branch circuit connected to ground and to the common point oli' said two branch circuits, the said auxiliary branch circuit including the primary of a coupling inductance coil and also including resistance, inductance and capacity elements so adjusted that the said auxiliary branch circuit has the same impedance as the antenna branch circuit, and a receiving circuit coupled by means of said coupling coils to both the antenna and the auxiliary branch circuits, the said receiving circuit being tuned to resof nance with the wave length of the received signals and being tuned to anti-resonance wizh the wave length of the transmitted sig na s. v

ln testimonyy whereof, l have signed my name to this specification in the presence of two subscribing witnesses,v this 22nd day of September, 1915.

I JOHN n oanson. 

